1. Field of the Invention
This invention relates to a process for installing synthetic fiber diaphragms in chlor-alkali cells, and more particularly it relates to such process in which the initial diaphragm resistance is reduced, thereby decreasing the start-up cell voltages.
2. Description of the Prior Art
The use of diaphragms in chlor-alkali cells is well known, and asbestos diaphragms have been used satisfactorily for many years. However, since asbestos is found to be a hazardous material, widespread efforts have been made to utilize substitute materials in the diaphragms. One satisfactory substitute which has been found and is known to the prior art is the use of relatively inert synthetic plastic material which may be formed into small fibers and deposited by known techniques to provide fibrous diaphragms. An example of such a diaphragm is shown in U.S. Pat. No. 4,036,729. Other improvements have been made in the use of these synthetic fibers to make satisfactory diaphragms, involving the use of fluorinated hydrocarbon resins, heat treatments, and the like in order to render the diaphragms more satisfactory.
However, these synthetic fibers are hydrophobic and have presented difficulties not present with hydrophilic asbestos fibers. Accordingly, it is also known to utilize surfactants to render the fiber diaphragms more wettable. Even with these improvements, it takes about two weeks of operation before the diaphragm heretofore in use begins to operate under satisfactory conditions.
U.S. Pat. No. 4,012,541 relates to a diaphragm made with polytetrafluoroethylene film in which it is suggested that air be removed by vacuum when the diaphragm is wetted. However, there is no suggestion of carrying out this step in a brine solution, and forcing conductive brine into the interstices of the diaphragm.